1. Field of the Invention
The present invention relates to the manufacture of composite cutting edges. More particularly, the present invention relates to the manufacture of cutting edges using ion etching and ion assisted processes.
2. Description of Related Art
Depending upon the application of a cutting implement, one or more factors may be important to the usefulness the cutting blade used in the implement. These factors can include the strength, toughness, sharpness, hardness, friction and corrosion resistance of the blade. Some prior art references have disclosed methods for producing blades that address some of these problems.
Use of a sputter etching technique to shape a blade edge has been described, for example in U.S. Pat. No. 5,056,227 by Kramer and U.S. Pat. No. 5,048,191 by Hahn. In the Kramer patent, a razor blade is formed by grinding a ceramic substrate with diamond abrasive and smoothing and honing the edge with diamond grit. To sputter the edge, the sputtering chamber is evacuated to a pressure equal to or better than 2.times.10.sup.-6 torr and argon is introduced to attain a sputtering gas pressure of 10 millitorr. 13.56 megahertz RF power is applied to establish a stable plasma with 200.degree. C. watts RF forward power. Using an argon plasma sheath that comes in from all directions, an etch duration of 2.5 minutes reduces the tip radius to about 200 Angstroms. Thereafter, the sputtering unit can be switched from etch mode to deposition mode and a chromium-platinum coating can be sputtered onto the edge by pre-sputtering a chromium-platinum target and depositing the released atoms on the blade edges. The Hahn patent discloses a similar process for use with single crystal substrates.
Other patents have suggested the use of implantation to modify the properties of the cutting edge. For example, U.S. Pat. No. 3,900,636 by Curry et al. discloses that the properties of a cutting edge, such as the hardness, can be improved by subjecting the edge to an ion implantation treatment. Curry et al. disclose a process for treating steel cutting edges by ion implantation using ions that either form compounds with the steel, such as H, B, C or N, or those that do not form compounds, such as Ti or Cr. The patent also discloses that inert ions can be implanted to increase the adhesion of the coatings. The ions impinge directly on the blade surface with an ion beam energy of between about 10 keV and 400 keV.
U.S. Pat. No. 3,915,757 by Engel discloses a process for forming an edge from a steel or iron containing substrate by implanting metal ions, such as titanium, zirconium, or the like, into the blade edge and hardening the edge by nitriding or carburizing the implanted ions. The blade is placed in an ion chamber and is cleaned with an argon plasma. A pool of molten metal is heated, the metal vaporizes and forms ions which are attracted to the blades since the blades function as the cathode. The first ions that strike the substrate are implanted until the surface becomes saturated, at which point the metal ions. plate the surface. The plating can then be carburized or nitrided to form a hardenable surface.
U.S. Pat. No. 3,894,337 by Jones discloses a method for making razor blades from a single crystal of alumina. The edge of the single crystal alumina can be shaped by bombardment with inert ions. It is disclosed that a substantially flat beam or a substantially cylindrical or conical beam can be used. In the case of cylindrical or conical beams, the beam of ions may be oscillated to form a wide beam. Thereafter, larger ions can be "stuffed" into the edge of the blade to increase the strength thereof. The large ions can be introduced into the single crystal alumina by ion implantation methods using beams of high energy ions, such as ions having an energy of about 10.sup.3 eV. Optionally, the razor blades may be coated, for example with chromium or nitrided metals or nittided alloys.